An integration of SAR time series, optical data and archival documentation for the identification of hypogea as a possible factor of vulnerability in Rome

In Rome, the expansion of urbanization, the increase of population density, and the subsequent escalation of traffic are common factors in road infrastructure vulnerability, especially when these aspects coexist with the presence of ancient subterranean environments, such as ancient tuff quarries. These wide networks of subterranean structures are often in endangered preservation conditions, also because their position and extension are only partially known. Furthermore, the aerial bombing attacks that the city of Rome experienced during the II World War are considered here as another critical factor favouring ground instability processes. In the present research, the joint exploitation of SAR dataset, "historical photograms", and vectorization of historical records have been applied on circumstanced test areas to estimate the quarries' dimension and typology and to evaluate their conservation state related to these anthropogenic aspects. The aims were addressed mainly with the twofold use of the SAR Cosmo-SkyMed dataset, from the processing of both intensity and phase information contents. The intensity has been used to distinguish low and high backscattering anomalies attributed to the presence of open cast and subterranean structures. The phase information was processed from SAR long time-series, through the PSInSAR method, to test its performance in monitoring cavity stability state. The extraction of Permanent Scatterers was carried out to evaluate its suitability to detect entities of displacement through a wide time span, especially using interpolation maps, to identifying patterns related to ancient hypogea. This stratification of information has been analyzed around endangered areas. Using this method to analyze the features mentioned, a relationship between these anthropic factors and sinkholes was revealed.